Residential reverse osmosis system

ABSTRACT

Some embodiments of the present invention relate to a reverse osmosis (RO) system that includes a housing and a pre-filter within the housing such that feed water flows into the housing and enters the pre-filter. The reverse osmosis (RO) system further includes a membrane element within the housing such that the pre-filtered water flows from the pre-filter and enters the membrane element and permeate exits the membrane element through the housing. In some embodiments, the housing includes a first end cap at one end and a second end cap at an opposing end such that feed water flows through the first end cap into the pre-filter and pre-filtered water flows from the pre-filter into the first end cap. In addition, the pre-filtered water may flow from the first end cap to the membrane element such that permeate exits the membrane element through the first end cap in order exit the housing.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is continuation of U.S. application Ser. No.12/208,368, filed Sep. 11, 2008 now U.S. Pat. No. 7,862,710 , which is adivision of U.S. application Ser. No. 10/524,155, filed on Jan. 30, 2006and issued on Apr. 7, 2009, as U.S. Pat. No. 7,513,996, which is a U.S.National Stage Filing under 35 U.S.C. 371 from International ApplicationNumber PCT/US2003/025408, filed Aug. 12, 2003 and published in Englishas WO 2004/014528 Al on Feb. 19, 2004, which claims the benefit of U.S.Provisional Application, Serial Number 60/402,754, filed Aug. 12, 2002,under 35 USC 119(e), which applications and publication are incorporatedherein by reference in their entirety. This application is related toPCT Application PCT/US 03/06587, filed Mar. 3, 2003 and to PCTApplication PCT/US 03/17527, filed Jun. 4, 2003, both of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to the field of filtration devices, and morespecifically to a system and apparatus for residential reverse osmosis(RO).

BACKGROUND

Consumers are becoming more concerned with the quality of their drinkingwater. When RO is used in a residential setting, a user desires to haveclean water on demand. However, typical RO systems for home use haveslow purified water output. Thus, typical RO systems utilize a holdingtank to store water.

For example, in a typical system, water is pulled from the water line.This water is run through a carbon prefilter (often a sediment prefilteris included as well). The water then runs through a reverse osmosismembrane element. The concentrate stream from the membrane element flowsto the drain, while the permeate water runs into a storage tank—usuallywith 1-2 gallon storage capacity. From the storage tank the permeatewater runs through a second carbon filter (a polishing filter), then toa separate faucet usually mounted on the kitchen sink. Because thesesystems are only capable of producing a small rate of permeate, thestorage tank is required on almost every system. Moreover, there areseveral component costs to these systems that limit the bottom linemanufacturing cost of these units, with the membrane element and storagetank representing the largest overall percentage.

Accordingly, what is needed is a low-cost, compact, full-featured,pumpless, and tankless RO system for residential use.

SUMMARY

A tankless reverse osmosis system which is capable of producing apermeate flow rate of at least 500 gallons per day (GPD) when the systemis operating under home reverse osmosis conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a schematic representation of an RO filtration systemaccording to one embodiment.

FIG. 1B shows a schematic representation of an RO filtration systemaccording to one embodiment.

FIG. 2A shows a perspective view of a housing assembly according to oneembodiment.

FIG. 2B shows another perspective view of the housing assembly of FIG.2A.

FIG. 3 shows a perspective view of the housing assembly of FIG. 2A withan endcap removed.

FIG. 4 shows a section view of the housing assembly of FIG. 2A.

FIG. 5 shows a perspective view of an endcap according to oneembodiment.

FIG. 6A shows a perspective view of an automatic shutoff valve accordingto one embodiment.

FIG. 6B shows a section view of the automatic shutoff valve of FIG. 6.

FIG. 7A shows a perspective view of a housing assembly according to oneembodiment.

FIG. 7B shows a cut-away view of a portion of the assembly of FIG. 7A.

FIG. 7C shows a bottom portion of a manifold assembly according to oneembodiment.

FIG. 7D shows a top portion of a manifold assembly according to oneembodiment.

FIG. 7E shows a perspective view of the housing assembly of FIG. 7A.

FIGS. 7F and 7G show front and back perspective views of a connectoraccording to one embodiment.

FIG. 8A shows an air gap faucet according to one embodiment.

FIG. 8B shows an air gap faucet according to one embodiment.

FIG. 9 shows a perspective view of a housing assembly according to oneembodiment.

FIG. 10 shows a schematic representation of a filtration systemaccording to one embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and that structuralchanges may be made without departing from the scope of the presentinvention. Therefore, the following detailed description is not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims and their equivalents.

DEFINITIONS

Home Reverse Osmosis Conditions: 65 psi average water pressure at themembrane surface, the feed water being 77 degrees Fahrenheit andconsisting of 500 ppm NaCl in water having a pH in the range of 7-8, themembrane system operating at 25% recovery.

% Recovery: The ratio of water in the membrane permeate to water in thefeed to the membrane element, expressed as a percentage.

% Passage: The parts per million of chloride ion in the permeate dividedby the parts per million of chloride ion in the feed, expressed as apercentage.

% Rejection: 100% minus % Passage

A-value: The term “A value” in the context of the present discussionrepresents the water permeability of a membrane and is represented bythe cubic centimeters of permeate water over the square centimeters ofmembrane area times the seconds at the net driving pressure representedin atmospheres and temperature normalized to 25 degrees C. An A value of1 is 10⁻⁵ cm3 of permeate over the multiplicand of 1 centimeter squaredof membrane area times 1 second of performance at a net driving pressureof one atmosphere. In the context of the present discussion, A valuesgiven herein have the following unit designation: 10⁻⁵cm3/(cm2.sec.atm.) or 10⁻⁵ cm/(sec.atm) at 25 degrees C.

Net Driving Pressure: The feed water pressure minus the osmotic pressuredifference between the feed water and the permeate water.

Membrane Flux: The amount of permeate that passes through a membrane,expressed in gallons of permeate per square foot of active membrane perday.

Membrane Element Flux: The amount of permeate that passes through amembrane element, expressed in gallons per day.

Membrane Element: A device that configures membrane in such a way thatthe feed and concentrate waters can be separated from the permeatewater.

High Flux Reverse Osmosis Membrane Element: A reverse osmosis membraneelement that provides more than 50 gallons of permeate per day whenoperated under Home Reverse Osmosis Conditions.

Membrane: A semipermeable material that is capable of retaining afraction of a component in a feed water, the component being either adissolved or a non-dissolved substance.

Reverse Osmosis Membrane: A membrane that is capable of at least 20%NaCl rejection when operated under Home Reverse Osmosis conditions.

Permeate Channel: The permeate flow channel in a membrane element thatmay include a permeate carrier.

Standard Kitchen Sink Cabinet: As used herein, a standard kitchen sinkcabinet has a depth (front to back) of 24 inches, a width of 36 inches,and a height of 34½ inches.

FIG. 1A shows a schematic representation of an RO system 20 according toone embodiment. In one embodiment, system 20 is a residential RO systemcapable of providing a sufficient, constant flow rate of filtered waterwithout requiring a tank or a pump. (It is noted that the system ispumpless if there is sufficient feed water pressure. However, certainfeatures of the present system are also usable with a pump in asituation where the line pressure is relatively low).

System 20 generally includes a RO housing assembly 21 and a faucet 28.Housing assembly 21 has an inlet to receive feedwater 5, which istypically at standard residential line pressure (typically between 45 to70 psi). The feedwater is directed through a pre-filter 106, then to oneor more filtering membrane elements 108, 110 which are connected inseries. Each element 108 and 110 includes a permeate outlet and aconcentrate outlet. The concentrate outlet of element 108 is fed intothe inlet of element 110. The concentrate outlet 15 includes a flowrestrictor 24. In one embodiment, the feed water line and permeateoutlet line are coupled to an automatic shutoff (ASO) valve 22 which isactivated by the pressure differential between the two lines. Thus, whenfaucet 28 is opened, the resulting pressure drop in the permeate lineopens ASO valve 22, which allows the input feed water to flow throughthe filtration elements 106, 108, and 110. A check valve 26 in thepermeate line restricts back-flow when the faucet is turned off.

In use, a saddle valve can be used for tapping into a cold water line.Then tubing is provided from the saddle valve to the inlet of assembly21. There is outlet tubing for the concentrate stream, running to faucet28, and outlet tubing for permeate stream 10 running to the faucet.

In various embodiments, tankless system 20 minimizes one or more of thefollowing problems with regular systems.

A typical RO system sold today uses carbon prefiltration to protect themembrane from damage by oxidants (such as chlorine and chloramines),found in many of the municipal water supplies. The resulting effect fromthe removal of these disinfectants is that there can be substantialbacterial growth in the storage tanks. A disinfectant needs to bereintroduced into the permeate supply after the storage tanks. This addsextra costs to the products.

However, because there is no storage tank in system 20, the issue ofbacterial contamination has been minimized Thus, one embodimenteliminates the need for post-filtration or other post-treatment afterthe water has passed through the membrane elements 108, 110.

Moreover, a typical system measures 13″×13″×5″ without the storage tank.The storage tank is approximately 10″ in diameter by 13″ tall. Thecombined system takes up a large amount of space within the kitchen sinkcabinet. Typical tankless system which have pumps to increase the netdriving pressure measure about 18″×15″×6″. In contrast, the design ofsystem 20 can be similar in size to a standard residential RO systemless the storage tank or the pump. Thus offering a more compact look andreducing the concern of the amount of space required underneath thesink.

Also, because this tankless RO design eliminates the need for many ofthe expensive components, the system can be developed with totalcomponent costs less than lesser performing systems.

The present tankless RO design concept eliminates the need for a storagetank and places shut-off valve 22 between the feed line and the permeateline. This helps eliminate most issues relating to poor recovery,rejection and flow. This is because Membrane Flux and % Rejection areboth dependent on pressure, with both generally increasing withincreasing pressure. Consequently, the Net Driving Pressure has a largeeffect on permeate amount and permeate quality. In general, a ReverseOsmosis Membrane will yield about twice the flux and improved chlorideion retention when operated at twice the Net Driving Pressure. When aReverse Osmosis Membrane that provides high retention of chloride ion isused, the % Passage will approximately be cut in half when the NetDriving Pressure is doubled. Consequently, tank-based RO systems thattypically provide a significant back pressure that results not only indecreased Membrane Flux but also yields decreased % Rejection. Thepresent tankless design concept allows the system to provide higher %Rejection, higher membrane flux, and run at much higher recovery thanprevious systems. Moreover, the present design promotes better specificcontaminant reductions. One such example would be nitrate/nitrite. Sincethe membrane rejection capability on these ions is pressure-dependent,by eliminating the effects of backpressure from the storage tank, system20 can provide better rejection of nitrate/nitrite for a longer periodof time.

Moreover, in most residential RO system designs, the shut-off valvecloses when the tank pressure is 50% the feed pressure. As the permeateis removed from the storage tank, the shut-off valve will re-open whenthe pressure in the tank drops approximately 33%. As an example, on aninstallation where the inlet pressure is 60 psi, the system will shutoff when the tank pressure is 30 psi. In a typical case where theosmotic pressure is 5 psi, the Net Driving Pressure just before theshutting down is only 25 psi (60 psi feed pressure minus 30 psi permeateback pressure from the tank minus 5 psi osmotic pressure), or only about42% of the feed water pressure. The diaphragm valve will open when aboutone gallon of permeate water is drawn from the tank, which results in atank pressure of about 20 psi. Thus, the Net Driving Pressure when thesystem restarts is only 35 psi (60 psi feed pressure minus 20 psipermeate back pressure from the tank minus 5 psi osmotic pressure), orabout 52% of the feed water pressure. Consequently, a typical homereverse osmosis membrane system operates at a Net Driving Pressure equalto only about half of the available feed water pressure.

Since the average consumer typically uses no more than about one gallonof permeate water at a time and since the Recovery has been preset to25% based on no permeate back pressure from the tank, in actual usagethese systems tend to run closer to about 12% recovery. This means thatfor every 1 gallon of purified water produced by a typical residentialRO system, about 7.5 gallons of water is sent to the drain. Moreover,because the actual average net driving pressure of these systems when inuse is fairly low, the true percent TDS rejection the consumer sees iswell below what the membrane is capable of doing. For example, a typicalRO membrane element which has a minimum NaCl rejection specification of96% will, under normal operating conditions, have an actual TDSrejection closer to 90%. The present design improves these aspects ofhome RO systems.

The present design and system 20 is more compact, costs less to make andservice, and provides better performance than previous products.

FIG. 1B shows a schematic representation of a filtration system 100according to one embodiment. In one embodiment, system 100 is aresidential reverse osmosis filtration system capable of providing asufficient, constant flow rate of filtered water without requiring atank or a pump. (As noted above, the system is pumpless if there issufficient feed water pressure. However, certain features of the presentsystem are also usable with a pump in a situation where the feed waterpressure is relatively low). As will be discussed below, system 100omits many of the component parts used in typical home RO systemscurrently, thus providing a lower manufacturing cost, less chance ofbreakdown, and an overall smaller size. Moreover, the present tanklessRO design concept provides numerous features defining a new paradigm forpoint-of-use filtration systems.

System 100 generally includes a RO housing assembly 102 and a faucet104. Housing assembly 102 has an inlet to receive feedwater 5, which istypically at standard residential line pressure (typically between 45 to70 psi). The feedwater is directed through a pre-filter 106, then to oneor more filtering membrane elements 108, 110 which are connected inparallel. Each element 108, 110 includes a permeate outlet 113, 114 anda concentrate outlet 116, 118, respectively. In one embodiment, theconcentrate outlet line and permeate outlet line are coupled to anautomatic shutoff (ASO) valve 112 which is activated by the pressuredifferential between the two lines. Thus, when faucet 104 is opened, theresulting pressure drop in the permeate line opens ASO valve 112, whichallows the concentrate to flow, and allows feedwater to flow through thefiltration elements 106, 108, and 110. The concentrate and permeateleave the assembly 102 and enter an air-gap faucet 104, where thepermeate is directed out of the faucet and the concentrate is sent tothe drain. The system can include electronics 122 within the assemblyand connected to various other members to perform analysis ofperformance of the system. Further details of each of these members willbe discussed below to better describe the present system.

In various embodiments, either system 100 or system 20 (FIG. 1A) can bemodified to be in parallel or series and can have an ASO valve betweeneither the feed and permeate lines or between the concentrate andpermeate lines. Moreover, in some embodiments a plurality of systems 20and 100 can be connected together. For example, a user can couple two ormore of systems 20 or systems 100, or a combination of the two, into anyseries or parallel flow configuration.

In use, a saddle valve can be used for tapping into a cold water line.Then tubing is provided from the saddle valve to the inlet of assembly102. There is outlet tubing for the concentrate stream, running to anair-gap on faucet 104, and outlet tubing for permeate stream running tothe faucet. The concentrate stream opens when faucet is turned on, thencloses when faucet is shut off. There is tubing from the air-gap faucetto a drain clamp for the concentrate stream.

In various embodiments, the present tankless system 100 minimizes one ormore of the following problems with regular systems.

In current systems, a shut-off valve is coupled to the feed water lineand the line to the storage tank and is regulated by the pressuredifferential between the feed line and the storage tank. When thestorage tank fills up, the backpressure exerted on a diaphragm in thevalve is enough to close the valve and thus close off the feed watersupply, thus shutting down the system. These valves are inherentlysusceptible to leaking at the various sealing areas. Also, theintroduction of small particles around the diaphragms can prevent thevalve from shutting off entirely, thus allowing water to run to draincontinuously. Another issue with present shut-off valves is their effecton recovery. This issue will be addressed later.

However, system 100 does not require the standard shut-off valve betweenthe feed line and a tank. In contrast, shut-off valve 112 is locatedbetween the permeate and the concentrate lines and is controlled by thefaucet, thus the potential for failures is greatly reduced. Also, theplacement of valve 112 provides better TDS rejection, produces a moreconsistent permeate flow, and runs at a higher recovery rate.

Another problem on previous systems is the check valve between thestorage tank and the membrane element. This check valve prevents theback-flow of water from the storage tank when the feed water is shutoff. Because the pressure in the tank (typically 30-40 psi), is greaterthan the pressure to drain (0 psi), when the system is shut off, asystem with a failed check valve allows the permeate water in thestorage tank to run back through the membrane and down the drain. Thiscreates two issues. The first is that the customer never has a storageof permeate water and the second is that the result of the back pressureexerted by the tank on the membrane element causes cracking of themembrane around the product water tube and leads to membrane failure.

However, since system 100 does not have the back pressure from a storagetank, no check valve is required—thus eliminating the check valve as apotential failure mode.

A typical RO system sold today uses carbon prefiltration to protect themembrane from damage by oxidants (such as chlorine and chloramines),found in many of the municipal water supplies. The resulting effect fromthe removal of these disinfectants is that there can be substantialbacterial growth in the storage tanks. A disinfectant needs to bereintroduced into the permeate supply after the storage tanks. This addsextra costs to the products.

However, because there is no storage tank in system 100, the issue ofbacterial contamination has been minimized. Thus, one embodiment doesnot require post-filtration or post-treatment after the water has passedthrough the membrane elements 108, 110.

The design of system 100 can be similar in size to a standardresidential RO system less the storage tank or the pump. Thus offering amore compact look and reducing the concern of the amount of spacerequired underneath the sink. Also, because this tankless RO designeliminates the need for many of the expensive components, the system canbe developed with total component costs less than lesser performingsystems.

As noted above, with the present tankless RO design concept eliminatingthe need for a storage tank and a shut-off valve positioned between thefeed line and the storage tank, most issues relating to poor recovery,rejection and flow are resolved. This is because Membrane Flux and %Rejection are both dependent on pressure, with both generally increasingwith increasing pressure. Consequently, the Net Driving Pressure has alarge effect on permeate amount and permeate quality. In general, aReverse Osmosis Membrane will yield about twice the flux and improvedchloride ion retention when operated at twice the Net Driving Pressure.When a Reverse Osmosis Membrane that provides high retention of chlorideion is used, the % Passage will approximately be cut in half when theNet Driving Pressure is doubled. Consequently, tank-based RO systemstypically provide a significant back pressure that results not only indecreased Membrane Flux but also yields decreased % Rejection. Thepresent tankless design concept allows the system to provide higher %Rejection, a higher membrane flux, and run at much higher recovery thanprevious systems. Moreover, the present design promotes better specificcontaminant reductions. One such example would be nitrate/nitrite. Sincethe membrane rejection capability on these ions is verypressure-dependent, by eliminating the effects of backpressure from thestorage tank, system 100 can provide better rejection of nitrate/nitritefor a longer period of time.

Moreover, in most residential RO system designs, the shut-off valvecloses when the tank pressure is 50% the feed pressure. As the permeateis removed from the storage tank, the shut-off valve will re-open whenthe pressure in the tank drops approximately 33%. As an example, on aninstallation where the inlet pressure is 60 psi, the system will shutoff when the tank pressure is 30 psi. In a typical case where theosmotic pressure is 5 psi, the Net Driving Pressure just before theshutting down is only 25 psi (60 psi feed pressure minus 30 psi permeateback pressure from the tank minus 5 psi osmotic pressure), or only about42% of the feed water pressure. The diaphragm valve will open when aboutone gallon of permeate water is drawn from the tank, which results in atank pressure of about 20 psi. Thus, the Net Driving Pressure when thesystem restarts is only 35 psi (60 psi feed pressure minus 20 psipermeate back pressure from the tank minus 5 psi osmotic pressure), orabout 52% of the feed water pressure. Consequently, a typical homereverse osmosis membrane system operates at a Net Driving Pressure equalto only about half of the available feed water pressure.

Since the average consumer typically uses no more than about one gallonof permeate water at a time and since the Recovery has been preset to25% based on no permeate back pressure from the tank, in actual usagethese systems tend to run closer to about 12% recovery. This means thatfor every 1 gallon of purified water produced by a typical residentialRO system, about 7.5 gallons of water is sent to drain. Moreover,because the actual average net driving pressure of these systems when inuse is fairly low, the true percent TDS rejection the consumer sees iswell below what the membrane is capable of doing. For example, a typicalRO membrane element which has a minimum NaCl rejection specification of96% will, under normal operating conditions, have an actual TDSrejection closer to 90%. The present design improves these aspects ofhome RO systems.

The present design and system 100 is more compact, costs less to makeand service, and provides better performance than previous products.

FIG. 2A shows a perspective, outside, view of housing assembly 102according to one embodiment. In one embodiment, housing assembly 102includes an elongated assembly body 202. In this example, assembly body202 includes a generally triangular cross-section and includes a firstendcap 204 and a second endcap 206 at each end of the body respectively.Assembly 202 endcap 206 includes a feedwater inlet 208 which isconnectable to a feed water line. Endcap 206 also includes permeateoutlet 210 and concentrate outlet 212. The triangular shaped endcap 206is removably mounted to the end of assembly body 202 by a singleretaining member such as an endcap nut 214. As will be discussed below,endcap 206 covers the ends of all the filter members and elements withinbody 202. Thus, the present design allows a single retaining member 214to be removed to provide access to all the filters. This greatly reducesthe time and effort required to change or check the filters.

FIG. 2B shows further details of endcap 204 of body 202. Endcap 204 hasa generally triangular shape to cover one end of assembly body 202. Inthis example, the system includes a set of indicators, such as one ormore status indicators 216 and 218. Indicators 216 and 218 can be LEDs,for example, mounted and exposed on endcap 204. These indicators can beused to indicate the condition of the filtration members within body202, indicating to a user when it's time to change the filters. In someembodiments, indicators 216 and 218 are mounted on other surfaces ofbody 202, or on endcap 206.

FIG. 3 shows a perspective view of housing assembly 102 with endcap 206removed. Here it can better be seen how filter 106, 108, and 110 areexposed once the endcap 206 is removed. Assembly body 202 includes acylindrical pre-filter chamber 306 which extends longitudinally down theassembly body. Similarly, a first membrane element chamber 308 and asecond membrane element chamber 310 are also cylindrical tubes runninglongitudinally down the body. As discussed above, these chamber areoriented such that body has a generally triangular cross-section.Assembly body 202 also includes a permeate outlet line 314 runninglongitudinally along the body and a concentrate outlet line 316 runninglongitudinally along the body. Outlet lines 314 and 316 bring theconcentrate and permeate up from the far end of assembly 102 and out ofassembly 102 through the permeate and concentrate outlets 210 and 212(FIG. 2A.) A mounting member 318 is used to mount with retaining member214 to mount endcap 206 to the housing assembly body.

In one embodiment, this assembly design is a molded design integrallyincorporating all flow lines and filter chambers with the body. Thisprovides efficient manufacturing as well as a small volume, smallfootprint design. Thus, the present assembly can fit under sinks withoutany problem. For example, one example assembly 102 has dimensions ofapproximately 21.25 inches long, 8.25 inches wide, and 7.63 inches high.Some examples have a longest dimension of approximately 35 inches orless, some are approximately 24 inches or less, some are approximately22 inches or less.

In one embodiment, the overall volume of the assembly, measured as thecontainer volume in which the assembly can be contained is approximatelythe size of a standard kitchen sink cabinet or smaller. In someembodiments, the volume in which the assembly can be contained is lessthan or equal to approximately 4500 cubic inches. In one embodiment, thevolume can be approximately 720 cubic inches or less; another embodimentis approximately 920 cubic inches or less; another is approximately 1500cubic inches or less; another embodiment is approximately 1700 cubicinches or less; another is approximately 2000 cubic inches or less.

In one example, shown in FIG. 9, an assembly 102B can have a crosssection where the filter elements define the outer dimension and thepermeate and concentrate channels are also the outside dimension,providing a minimum volume concept such that the element cartridgehousings are the assembly. Thus, in one embodiment, the present systemcan include one or more housings having a total displacement volume ofless than or equal to approximately 668 cubic inches. Moreover, sincethe present design eliminates the need for pumps or storage tanks, theassembly is the only unit between the feedwater line and the faucet.

Prefilter 106 is mounted within chamber 306. Pre-filter 106 can be acarbon filter, and/or a sediment filter. Filter elements 108 and 110 areconfigured to provide a parallel flow arrangement through the system. Inother words the output of prefilter 106 communicates with both theinlets of filters 108 and 110.

In one embodiment, filters 108 and 110 are high flux RO membrane filterelements. These high flux membrane elements help eliminate the need fora reservoir tank for the system and help eliminate the need for any pumpto pressure the feedwater through the system. Some RO membrane elements108 and 110 have a spiral wound membrane element which includes a firstmembrane sheet and a second membrane sheet separated by a permeatecarrier. In one embodiment, the spiral wound membrane elements 108 and110 can be dimensioned to have a diameter of approximately 2.5 to 3inches or less and a length of approximately 18 inches or less. Invarious examples, to be discussed below in detail, the elements can beadapted to have various sizes, leaf numbers, and flow rates, anddifferent numbers of elements can be provided in the system. One exampleprovides a permeate flow rate of at least 75 GPD. Other examples haveflow rates of at least 250 GPD, at least 500 GPD, at least 700 GPD, andat least 750 GPD, and at least 1500 GPD. In some examples only one ROmembrane element is provided, or a pair of elements are connected inseries. Membrane elements 108 and 110 can be single-leaf or multi-leafdesigns. One embodiment has a diameter of approximately 6 inches or lessand a length of approximately 18 inches or less. One example has adiameter of 3 inches or less. One example has a diameter ofapproximately 2.5 to 3 inches. One embodiment uses a single-leaf ormulti-leaf spiral wound design as described in PCT Application PCT/US03/17527. Some embodiments use a membrane formed as described in PCTApplication PCT/US 03/06587. Further details of membrane and elementdesign will be discussed below.

FIG. 4 shows a section view of the housing assembly 102. As water flowsthrough assembly 102, the feedwater first enters through inlet 208. Thefeedwater enters into the chamber of pre-filter 106 and after beingfiltered the filtered water enters into molded passages 402 in theendcap. These molded passages bring the filtered water to membraneelements 108 and 110. The permeate exits through the end of the membraneelement into a molded passage 404 in endcap 204. The concentrate entersinto passages 406 in the endcap. The permeate and concentrate then gothrough opposite sides of ASO valve 112 and through lines 314, 316 (FIG.3), and exit through the permeate and concentrate outlets of endcap 206.Accordingly, all the flow within assembly 102 is either throughfiltering members 106, 108, 110, or through molded portions of assembly102 such as molded passages in the endcaps and molded concentrate andpermeate lines 314 and 316. Again, this design feature provides for acompact design with less worry of breakage, etc. Moreover, by using amolded design and by utilizing the endcaps of both ends of the assemblyas flow devices, the present assembly lessens the length needed withoutincreasing the footprint of the device.

FIG. 5 shows further details of endcap 204 according to one embodiment.Permeate passages 404 begin in the center of chamber endcap portions 502and 504. Shut off valve 112 is positioned to receive the permeate withina passage 506 after the permeate has gone though the passages in theendcap. Similarly, passage 508 receives the concentrate. In thisembodiment, ASO valve 112 is positioned to operate on the concentrateand permeate lines. The benefits of this arrangement are discussedabove. By sensing the pressure in the permeate line, the valve preventsconcentrate flow and flow through the system when the faucet is notturned on.

FIGS. 6A and 6B show a perspective view and a section view,respectively, of automatic shutoff valve 112 according to oneembodiment. The valve includes a sensor such as reed switch 602 todetect flow though the valve, as will be discussed below. Valve 112includes a permeate flow passage 720 and a concentrate flow passage 710separated by a diaphragm 704 which is actuated by the pressuredifferential between the permeate and concentrate lines. When a useropens the faucet at the outlet of the permeate flow, it lowers thepressure in permeate flow passage 720, which causes the diaphragm tomove upward, thus opening concentrate line passage 710. This allowsfluid to flow through the system.

A spring 702 urges the diaphragm against the opening 706 of a portion ofconcentrate flow passage 710. This keeps the valve in a normally closedposition to ensure positive shut off of the valve when the pressuredifferential between the permeate outlet line and the concentrate outletline causes the valve to close (i.e., when the faucet is turned off).Valve 112 includes a magnet carrier 722 and a magnet 724 positionedabove the diaphragm. Magnet 724 is positioned within the automaticshutoff valve such that the magnet activates reed switch 602 when theautomatic shutoff valve is open (i.e. when the faucet is opened). Reedswitch can be operatively coupled to a control circuitry 726 to provideinformation about the system to a controller or directly to a user. Inone example, diaphragm 704 is a rolling diaphragm which providessensitive movement to better control flow through the valve. The rollingdiaphragm also allows a smooth, easy travel, as opposed to typicalo-ring pistons which have a higher resistance to movement.

Again, due to the location of the ASO valve 112 in system 100, and thepumpless and tankless nature of the present system, the system providesa constant recovery rate. Moreover, when the faucet is opened there is asubstantially constant rate of flow of permeate through the faucet.Also, the present system provides that the ASO valve, and thus flowthroughout the system, is activated by the user opening and closing thefaucet.

FIG. 7A shows a perspective, outside view of a housing assembly 730according to one embodiment. In one embodiment, housing assembly 730includes a manifold 732, one or more filter cartridge housings 734, 736,and 738, and a base leg 740. A connector 742 is connected to manifold732 and includes a quick-connect fitting on the portion coupled to themanifold and push-in fittings, such as John Guest brand fittings, whichare connectable to tubes to bring feed water into manifold 732, andwaste and permeate water away from the manifold. In one embodiment,housing assembly has dimensions of approximately 17 inches high (top tobottom in FIG. 7A), 11 inches deep, and 21 inches wide (left to right inFIG. 7A). This allows the assembly to fit within a rectangle spacehaving a volume of approximately 4000 cubic inches or less. In someexamples, the assembly can be dimensioned to fit within a rectangularspace having a volume of approximately 4500 cubic inches or less. Otherexamples can vary the dimensions as desired, and as discussed above forhousing assembly 102.

Manifold 732 includes internal molded fluid passages to control the flowof water through the system, as will be discussed below. In thisexample, manifold 732 includes a generally triangular shape having awider bottom 746 than top 748. Similarly, base leg 740 has a generallytriangular shape. These shapes allow the assembly to rest solidly on asurface when orientated as shown in FIG. 7A. Alternatively, the assemblycan be orientated such that base-leg 740 is on the bottom and cartridgehousings 734, 736, and 738 extend upwardly, or manifold 732 can be onthe bottom and the cartridge housings can extend up towards the base leg740.

In one embodiment, cartridge housing 738 includes a pre-filter element,while cartridge housings 734 and 736 include RO elements configured ineither a parallel or series flow path, as explained above in FIGS. 1-3.

Base leg 740 is a plastic molded member which provides support for thedistal ends of cartridge housings 734, 736, and 738. Base leg 740 isremovable from the cartridge housings. Base leg 740 can include one ormore holes or indents 750, 752, and 754 to hold the ends of thecartridge housings. In one example, a wrench portion 756 is incorporatedinto one of the holes. Wrench portion 756 is an elongated cylindricalsection which includes tabs or other gripping features internally. Thesetabs engage the raised ridges 758 on cartridge housings 734, 736, and738 to allow leg-base 740 to be used as a wrench to either tighten orremove the cartridge housings from manifold 732. For example, FIG. 7Eshows how base leg 740 can be removed from cartridge housings 734, 736and 738, and then wrench portion 756 can be slipped over one of thecartridges to be used as a wrench to tighten or loosen the chosencartridge.

In one embodiment, connector 742 is a unitary member including threeinternal passages for feeding water to and receiving waste and permeatewater from the manifold. A locking member 744 engages the connector tokeep it in place. In other embodiments, three separate connectors can beused to attach the system to outside components.

FIG. 7B shows a cut-away view of a portion of assembly 730. Each ofcartridge housings 734, 736, and 740 are threaded to a socket on a lowersurface of manifold 732. In this example, cartridge housing 738 encasespre-filter 106 and cartridge housing 736 encases element 108.

FIGS. 7C and 7D show a top 762 and bottom 760 of manifold 732 accordingto one embodiment. In this example, all the fluid passages of manifold732 are molded into bottom 760 with top 762 covering them when the twoparts are attached together. In some embodiments, top 762 can includepassages either separately or as mating passages to be combined with thepassages of bottom 760. Some embodiments provide a manifold formed outof three or more separate members combined together.

In this example, manifold 732 provides a series flow through themembrane elements. Feed water enters through input port 764 and entersthe pre-filter located at socket 766. The pre-filtered water then goesdown passage 768 to enter the membrane located at socket 770. Thepermeate flows out of port 772 while the concentrate flows throughpassage 774 to the membrane element at socket 776. From there thepermeate flows out through outlet port 778 while the concentrate flowsout outlet port 780. Again, other configurations provide for a parallelflow through the membrane elements.

FIGS. 7F and 7G show a connector 782 according to one embodiment. Inthis example, connector 782 includes two or more separate connectormembers 784, 785, and 786. Each connector includes a first endconnectable to a hose or tube and a second end for connecting to one ofthe ports of manifold 732 of the housing assembly. The members 784, 785,and 786 can be separately removed and attached to the housing assembly.They are configured such that a locking key 790 holds the connectormembers in position on the inlet and outlet ports in a polarizedconfiguration. For example, the members 784, 785, and 786 can havedifferent diameters and locking key 790 can include grip or lockingportions 787, 788, and 789 dimensioned to fit specific ones of members784, 785, and 786. In one example, each of the connecting members caninclude one or more mating protrusions to mate with adjacent matingprotrusions on adjacent members.

FIG. 8A shows a faucet 104 according to one embodiment. Faucet 104 canbe an air-gap faucet which includes a permeate inlet 802 and aconcentrate inlet 804. The concentrate 15 crosses the air-gap and goesdown the drain. The permeate 10 goes through the faucet. An actuator 810allows a user to control the faucet. A set of indicators, such as a pairof indicators 806 and 808, indicate to a user the status of the system.Indicators 806 and 808 can be LEDs for example. This allows a user toknow the status without having to look at the indicators on the housingassembly. In one example use, the indicators 806 and 808 on the faucetindicate either “good” or “bad” without giving details. The user canthen check the housing assembly light indicators 216, 218 (See FIG. 2B)to check on the problem. The assembly lights can then indicate that aspecific filter needs to be changes for example. In one example, byproviding indicator light sets on both the faucet and the assembly thepresent system can be incorporated into a refrigerator unit. Suchrefrigerator units omit the faucet 104, thus this dual light systemallows a user to still check the status of the system by checking thehousing assembly.

In one embodiment, permeate inlet 802 has a ¼″ inner diameter andconcentrate inlet 804 has a ⅜″ inner diameter, and concentrate outlet 15has a ⅜″ inner diameter. The larger than typical diameter of theconcentrate inlet and outlet allows for the increased concentrate flowthrough the system which is caused by the high flux membrane. Oneembodiment uses a faucet 104 without an airgap and the air gap islocated remote from the faucet.

FIG. 8B shows an airgap faucet according to one embodiment where thefaucet includes an actuator 810 which has a built-in concentrateshut-off. This example can omit the ASO valve within assembly 102.

Various other embodiments of faucets can be used in the present system.In one example, the ASO valve can be incorporated in the faucet andcoupled to the concentrate and permeate inlets. One example can utilizea solenoid shut-off within the faucet. One example puts electronics 122(See FIG. 1) within the faucet.

Referring again to FIG. 1, electronic monitoring systems can beavailable on system 100. For example, electronics 122 can be coupled tothe reed switch of the ASO valve and detect each time the valve isopened or closed, thus allowing the system to know how long the systemhas been in actual use. This information can be used to predict when thepre-filter needs to be changed. TDS (total dissolved solids) sensors canbe coupled to the feed line and the permeate line for comparison. Thisinformation can be used to tell a user when to change the membraneelements. The electronics can also cause the indicator lights on theassembly or faucet to display as needed, as described above. Forexample, displaying when the filter and membrane element need to bechanged. In some examples, each electronic system can consist of: 1) anelectronic clock that displays every 6 or 12 months that filters needreplacing and; 2) a TDS monitor that uses conductivity sensors tocompare inlet TDS versus outlet (permeate) TDS and notifies the userwhen the % Rejection drops below a certain value (for example, 75%Rejection). Indicators, such as LEDs, LCDs, etc. can be mounted at thefaucet and on the assembly and light up to show when elements needchanging.

FIG. 10 shows a filtration system according to one embodiment. System1000 includes a single membrane element 108 within an assembly. Theelement can be formed as will be discussed below. A pre-filter 106 isconnected to the assembly inlet. An ASO valve 112 is connected to thepermeate and concentrate lines as discussed above. In one embodiment,system 1000 can be a disposable system in which the housing assembly isuncoupled from the feed line 5 and the outlet lines and replaced with afresh system.

Example Membranes

Examples of RO membranes usable in a membrane element of the presentsystem can be prepared by the following methods. One method forpreparing a reverse osmosis membrane having improved flux propertiesincludes treating a starting reverse osmosis membrane withdipropylammonium nitrate, diisopropylethylammonium nitrate,triethylammonium nitrate, tetraethylammonium nitrate, diethylammoniumnitrate or tetraethylammonium borate, or a mixture thereof (andoptionally drying) to provide a reverse osmosis membrane having improvedflux properties. One method of improving the permeability of a reverseosmosis membrane includes treating a reverse osmosis membrane with anaqueous solution of an organic nitrate or borate salt, drying; andoptionally recovering the membrane.

Reverse osmosis membranes which can be treated according to the methodsdescribed herein include the reaction product of polyacyl halides,polysulfonyl halides or polyisocyanates and polyamines or bisphenols.The reaction product is typically deposited within and/or on a poroussupport backing material.

Reverse osmosis membranes can be prepared using methods that aregenerally known in the art, for example using methods similar to thosedescribed in U.S. Pat. Nos. 3,744,642; 4,277,344; 4,948,507; and4,983,291. Such methods entail coating an aqueous solution of apolyamine or a bisphenol, and preferably a polyamine, on a poroussupport backing material. Thereafter, the surface of the coated supportmaterial is optionally freed of excess amine solution and is contactedwith an organic solution of a polyacyl halide, polysulfonyl halide orpolyisocyanate to provide the reverse osmosis membrane, which can beutilized as a starting material in the method of the invention. Thesemembranes may further be dried from glycerin, or drying agents disclosedin aforementioned patents.

The porous support backing material typically comprises a polymericmaterial containing pore sizes which are of sufficient size to permitthe passage of permeate therethrough, but are not large enough so as tointerfere with the bridging over of the resulting ultrathin reverseosmosis membrane. Examples of porous support backing materials which maybe used to prepare the desired membrane composite of the presentinvention will include such polymers as polysulfone, polycarbonate,microporous polypropylene, the various polyamides, polyimines,polyphenylene ether, various halogenated polymers such as polyvinylidenefluoride, etc.

The porous support backing material may be coated utilizing either ahand coating or continuous operation with an aqueous solution ofmonomeric polyamines or to render the resulting membrane more resistantto environmental attacks of monomeric secondary polyamines. Thesemonomeric polyamines may comprise cyclic polyamines such as piperazine,etc.; substituted cyclic polyamines such as methyl piperazine, dimethylpiperazine, etc.; aromatic polyamines such as m-phenylenediamine,o-phenylenediamine, p-phenylenediamine, etc.; substituted aromaticpolyamines such as chlorophenylenediamine,N,N′-dimethyl-1,3-phenylenediamine, etc.; multi-aromatic ring polyaminessuch as benzidine, etc.; substituted multi-aromatic ring polyamines suchas 3,3*-dimethylbenzidine, 3,3*-dichlorobenzidine, etc.; or a mixturethereof depending on the separation requirements as well as theenvironmental stability requirements of the resulting membranes.

The solution which is utilized as the carrier for the aromatic polyaminewill typically comprise water in which the aromatic polyamine will bepresent in an amount in the range of from about 0.1 to about 20% byweight of the solution and which will have a pH in the range of fromabout 7 to about 14. The pH may either be the natural pH of the aminesolution, or may be afforded by the presence of a base. Some examples ofthese acceptors will include sodium hydroxide, potassium hydroxide,sodium carbonate, triethylamine, N,N′-dimethylpiperazine, etc. Otheradditives in the amine solution may include surfactants, amine salts(for example see U.S. Pat. No. 4,984,507), and/or solvents (for examplesee U.S. Pat. No. 5,733,602).

After coating the porous support backing material with the aqueoussolution of the aromatic polyamine, the excess solution is optionallyremoved by suitable techniques. Following this, the coated supportmaterial is then contacted with an organic solvent solution of thearomatic polyacyl halide. Examples of aromatic polyacyl halides whichmay be employed will include di- or tricarboxylic acid halides such astrimesoyl chloride (1,3,5-benzene tricarboxylic acid chloride),isophthaloyl chloride, terephthaloyl chloride, trimesoyl bromide(1,3,5-benzene tricarboxylic acid bromide), isophthaloyl bromide,terephthaloyl bromide, trimesoyl iodide (1,3,5-benzene tricarboxylicacid iodide), isophthaloyl iodide, terephthaloyl iodide, as well asmixtures of di-tri, tri-tri carboxylic acid halides, that is, trimesoylhalide and the isomeric phthaloyl halides. Alternative reactants to thearomatic polyacyl halide include aromatic di or tri sulfonyl halides,aromatic di or tri isocyanates, aromatic di or tri chloroformates, oraromatic rings substituted with mixtures of the above substituents. Thepolyacyl halides may be substituted to render them more resistant tofurther environmental attack.

The organic solvents which are employed in the process described hereinwill comprise those which are immiscible with water, immiscible orsparingly miscible with polyhydric compounds and may comprise paraffinssuch as n-pentane, n-hexane, n-heptane, cyclopentane, cyclohexane,methylcyclopentane, naphtha, Isopars, etc. or halogenated hydrocarbonsuch as the Freon series or class of halogenated solvents.

A reverse osmosis membrane, for example a membrane prepared as describedabove, is exposed to dipropylammonium nitrate, diisopropylethylammoniumnitrate, triethylammonium nitrate, tetraethylammonium nitrate,diethylammonium nitrate or tetraethylammonium borate, or a mixturethereof for a period of time ranging from about 1 second to about 24hours. The exposure of the membrane is usually affected at temperaturesranging from ambient up to about 90 degrees C. or more and preferably ata temperature in the range of from about 20 degrees to about 40 degreesC.

Following exposure of the membrane, it is dried at elevated temperature(up to about 170 degrees C.) for a period of time ranging from about 30seconds to about 2 hours or more in duration.

Representative Membrane Elements

A spiral wound element is comprised of a leaf, or a combination ofleaves, wound around a central tube with a feed spacer material. Eachleaf is a combination of two membranes with a permeate carrier placedbetween the membranes. The region between the two membrane sheets iscalled the permeate channel. The leaf package is sealed to separate thepermeate channel, with part of the permeate channel unsealed to allowfor removal of the permeate fluid. For instance, in a spiral-woundmembrane element, three sides of the leaf are typically sealed, whilethe fourth side of the leaf is typically connected to a permeate tube.The leaf length is defined as the longest straight-line distance ofpermeate flow to the permeate collection channel.

Spiral-wound membrane elements are relatively inexpensive to produce. Asingle-leaf membrane element is much simpler and less costly to producethan membrane elements that contain multiple leaves. Each extra leafused in a membrane element reduces the maximum amount of area that canbe placed in an element having specific dimensions because theadditional leaves require additional glue lines and also because thetypical fold of a leaf at the permeate tube is often sealed and canaccount for lost active membrane area. Further, additional leaves in amembrane element lead to a higher likelihood of element failure becauseof improperly placed leaves during element fabrication and also becausehigher amounts of leaves make it more difficult to produce a uniformlyround element.

An ultra high flux RO membrane prepared as discussed above provides awater permeability that is nearly three times as great as thepermeability of brackish water RO membranes and provides about 75%greater permeability than “low pressure” RO membranes. The ultra highflux RO membrane has extremely high pure water permeability.

The permeate carrier's function is to provide a channel for the permeateto flow through on its way to the permeate tube. The permeate carriermust be able to effectively keep the adjacent membranes from intrudinginto the permeate channel and must provide a relatively low resistanceto permeate flow. Any pressure build-up in the permeate channel willcause an equal reduction in the net driving force of the membraneprocess. The net driving force to the membrane is defined as thepressure in the feed channel minus the osmotic pressure and minus thepermeate pressure.

In most home reverse osmosis applications, the typical amount of averagepressure loss in the permeate channel is low relative to the net drivingpressure. Consequently, the pressure loss in the permeate channel doesnot overly affect the overall output of the membrane element. However,when a membrane element is produced that uses the newly developed highflux membranes discussed above, the resulting high membrane flux ratesleads to a significant pressure loss in the permeate channel can have amajor impact on the total element output. Moreover, the salt rejectingability of RO membranes is directly related to the driving pressure,with higher driving pressures leading to higher salt rejection.Therefore, the permeate side pressure loss does not only reduce membraneflux but also increases the salt passage through the membrane.

In one embodiment, the present system utilizes new permeate carriermaterials that have a lower resistance to flow and therefore provideimproved element flux and reduced salt passage. Further, because thenewly developed high flux membranes can operate at low pressures, thepermeate carrier does not need to maintain the integrity of the permeatechannel at the high pressures required by current reverse osmosismembranes.

Permeate Channel Design

For a given feed solution where the viscosity is fixed, the H value of apermeate channel is dependent on the friction factor and the thicknessof the permeate channel. Thus to minimize the H value of a permeatechannel its thickness can be increased. However, as elements are oftendesigned to fit within pressure vessels of fixed diameter, increasedpermeate channel thickness necessitates the use of less membrane area.As less membrane area reduces the element flow, other strategies tolower the H value are desirable.

The friction factor reflects pressure drop from flow through thepermeate channel due to several factors, including: friction with thepermeate carrier surfaces, turbulence promoted by the channel geometry,and other permeate carrier design factors that are independent ofthickness Improved H values obtained through decreased friction factorsallows thinner and more efficient permeate carriers to be used. Thuspermeate carriers with lower friction factors would be highly useful.

The friction factor of a permeate carrier can most easily be decreasedby increasing the size of the channels it contains. However, in additionto transporting permeated fluid, the permeate carrier needs to supportthe membrane against the hydraulic pressure used to drive theseparation. If the permeate carrier is unable to properly support themembranes, the permeate channel thickness will be reduced, leading tohigher permeate channel pressure drop and also may lead to elementdeformation. In the past, low membrane A-values (<20) have required theuse of high net driving pressures (>100 psi) to obtain reasonable fluxesand as a result, relatively dense permeate channels were required tosupport the permeate carrier from compaction. These dense channels havea high resistance to flow and thus give high H values. However, becausethe applied pressure was significantly high relative to the pressurebuild-up in the permeate channel, the membrane elements yielded arelatively high β term.

Accordingly, with new higher flux membranes, use of existing permeatecarriers proved difficult as poor efficiencies were obtained. However,as lower operating pressures are used with these membranes it was foundthat new types of permeate carriers could now be used which hadrelatively wide channels. These provided low H values while stillsupporting the permeate channel at the pressures used.

The permeate carriers effective for use in these elements are unique byvirtue of their low H value for a given thickness. Two examples are apermeate carrier having an H-value of approximately 0.01 (AtmSec/cm3)with a thickness of approximately 13 mils (an example is Naltex75-3719), and a permeate carrier having an H-value of approximately0.026 (AtmSec/cm3) with a thickness of approximately 20 mils (an exampleis Naltex S-1111). The permeate carriers are also unique in that theyprovide low resistance while being thin, yet are still able to supportthe permeate channel from significant intrusion by the membranes.

In other embodiments, the permeate carrier can be made of any suitablematerial having the flow resistance characteristics (e.g. H values)described herein, provided the material is capable of suitablysupporting the permeate channel under operating conditions. For example,the permeate carrier can be made of metal (e.g. stainless steel),ceramic, or an organic polymer (e.g. nylons, polypropylenes, polyesters,or coated polyesters). Suitable materials have previously been utilizedin a variety of applications, for example as feed spacers inspiral-wound reverse osmosis elements (feed spacers for reverse osmosisare typically 17 mils thick or greater, with some exceptions allowingfor feed spacers as thin as 13 mils to be used), as supports for pleatedfilters (6-mil to about 20-mil thick spacers are commonly used in theseapplications), as covering for depth filtration media to prevent themedia from migrating (6-mil to about 20-mil thick spacers are commonlyused in these applications), as HVAC screens in the automotive industry,or as tank liners. Accordingly, such materials are commerciallyavailable. Additionally, materials having the desired thickness andpermeability properties can be prepared for use in the materials andmethods of the invention. In various embodiments, membrane elements canbe formed having a permeate channel H-value of approximately 0.10, orapproximately 0.10 or less. Some embodiments, have a permeate channelH-value of approximately 0.06, or approximately 0.06 or less. Variousembodiments utilize membranes having an average A-value of approximately16 or greater; an average A-value of approximately 22 or greater; anaverage A-value of approximately 25 or greater; an average A-value ofapproximately 30 or greater; and an average A-value of approximately 35or greater.

EXAMPLES

Membrane elements can be formed with various geometries depending onlength, width, and performance characteristics desired. The presentsystem allows for the use of optimized sized elements for use in apoint-of-use system. Many different sizes and characteristics will beusable with the present system. Accordingly, the following examples aregiven for illustration and are not limiting.

Example 1

Sample membrane elements were formed having the following specificationsand were tested with the results as shown:

Flow, gpd Sample# @77 F. % Rejection 1 227.07 93.6% 2 234.62 94.8%Element Specifications

#Leafs 1 Permeate Carrier H- .06 value Flat Sheet A-value 23.9 FlatSheet Rejection (%) 97 Dimensions (in) Scroll Width 18 Diameter 2.4 FeedSpacer Thickness 21 (mils) Permeate Carrier 13 Thickness (mils) LeafLength (ft) 6.4 Tube OD (in) 1 β (Efficiency %) 74.5Test Conditions (Element)

Pressure (psig) 65 Pressure output (psig) 41 Feed Cond (uS) 1082 FeedConc (ppm) 534 Feed T (deg F.) 75.56Test Conditions (Flat Sheet)

Pressure (psig) 100 Feed Conc (ppm) 500 Feed T (deg F.) 77

Example 2

Theoretical optimized 2 element design @ 65 psi, 500 ppm NaCl/RO

25% recovery 360GPD/element

Element Specifications

#Leafs 1 PC H-value .03 Flat Sheet A-value 30 Flat Sheet Rejection (%)97 Dimensions (in) Scroll Width 18 Diameter 2.6 FS Thickness (mils) 21PC Thickness (mils) 13 Leaf Length (ft) 6.9 Tube OD (in) 1 β (Efficiency%) 81.2Test Conditions

Pressure (psig) 65 Pressure output (psig) 65 Feed Conc (ppm) 500 Feed T(deg F.) 77Test Conditions (Flat Sheet)

Pressure (psig) 100 Feed Conc (ppm) 500 Feed T (deg F.) 77

Example 3

Theoretical optimized 1 element design @ 65 psi, 500 ppm NaCl/RO

25% recovery 720GPD/element

Element Specifications

#Leafs 8 PC H-value .06 Flat Sheet A-value 30 Flat Sheet Rejection (%)97 Dimensions (in) Scroll Width 13 Diameter 3.7 FS Thickness (mils) 21PC Thickness (mils) 13 Leaf Length (ft) 1.7 Tube OD (in) 1 β (Efficiency%) 96.9Test Conditions

Pressure (psig) 65 Pressure output (psig) 65 Feed Conc (ppm) 500 Feed T(deg F.) 77Test Conditions (Flat Sheet)

Pressure (psig) 100 Feed Conc (ppm) 500 Feed T (deg F.) 77

Sample systems were also formed with the following specifications andwere tested with the results shown:

Example 4

In this example, two high-flux membrane elements having thespecifications noted below were placed in an assembly of a tank-lessresidential reverse osmosis system. The system consists of a Ø3″×10″ GACpre-filter in a 10″ sump housing, two high-flux membrane elements inindividual element housings, automatic shutoff valve, a fixed orificeconcentrate flow restrictor, a home reverse osmosis drinking waterfaucet, and the necessary tubing and fittings to make fluid connectionsto a feed water source, drain, and drinking water faucet. The membraneelements were connected in series. The automatic shutoff valve is aspring biased pressure sensing diaphragm valve. The valve operates onthe concentrate flow of the second element with control input from thepermeate pressure.

Both membrane elements were tested prior to assembly into the examplesystem, under the following conditions: 50 psi feed pressure, 77° F.,500 ppm NaCl, 25% recovery, with the results below.

The example system was tested under the following conditions: 45 psifeed, 65° F., 540 μs feed conductivity, 22% recovery. The systemproduced 518 GPD permeate at 92% rejection. When the results arenormalized to home reverse osmosis conditions, adjusting for net drivingpressure, osmotic pressure and temperature, the system is projected toproduce 1021 GPD at 92% rejection.

System Specifications

Housing 1451 in³ Assembly Volume Length  21.5″ Width   9″ Depth   7.5″Element #1 A-value  26 H-value   .03 Rejection  93% Diameter   2.9″Length  18″ Element #2 A-value  36 H-value   .03 Rejection  90% Diameter  2.9″ Length  18″

As is seen from the examples above, by utilizing a membrane as discussedherein and by modifying various membrane element specifications (size,number of leafs, etc), a pumpless, tankless RO system can be designedwhich is optimized for one or more design features, such as overall sizeand output. For example, by utilizing high-flux membranes with anappropriate permeate carrier, one or more elements can be placed in ahousing assembly having an overall volume small enough to fit within astandard kitchen sink cabinet. Such assemblies can further be connectedtogether in series or parallel if desired. Systems can be built having apermeate flow rate of at least 500 GPD when the system is operatingunder home reverse osmosis conditions; a permeate flow rate of at least750 GPD; and a permeate flow rate of at least 1000 GPD.

Moreover, the present pump-free tankless residential RO system can bemore compact, have less service issues, cost less and provide betterperformance than existing products. The system can be mounted underneatha kitchen sink using a minimum amount of space. Moreover, the hardwareassociated with current designs (i.e. storage tank, shut-off valvelocation, and check valve) will not be needed thus decreasing costs andspace requirements while increasing reliability. Although the presentdiscussion describes a high flow, pumpless, tankless RO system, someembodiments could incorporate either of those items if desired.

In various embodiments, the discussion and features discussed herein canbe combined and modified to provide for various home RO systems. Forexample, one embodiment can a tankless reverse osmosis system which iscapable of producing a permeate flow rate of at least 500 GPD when thesystem is operating under home reverse osmosis conditions and isdimensioned to fit within a standard kitchen sink cabinet. In oneembodiment, the present system can include a housing assembly having aninlet to receive feed water, a pre-filter coupled to the inlet toreceive the feed water, the pre-filter having an outlet, a membraneelement to receive the feed water from the outlet of the pre-filter, themembrane element having a permeate output and a concentrate outlet, anda faucet to receive filtered water from the permeate outlet, whereinthere is not an intervening storage tank between the membrane elementand the faucet, wherein the membrane element is capable of producing atleast 500 GPD under home reverse osmosis conditions and wherein themembrane element is enclosed within a housing assembly dimensioned tofit within a standard kitchen sink cabinet.

In one embodiment, the system can include a housing assembly, an inleton the assembly to receive feed water, a prefilter member communicatingwith the inlet to receive the feed water from the inlet, and a membraneelement communicating with an outlet of the prefilter to receive thefeed water from the prefilter member, the membrane element having aconcentrate outlet and a permeate outlet, wherein the permeate outlet isconnected to a faucet without an intervening storage tank, wherein themembrane element includes a spiral wound membrane element which includesa first membrane sheet and a second membrane sheet separated by apermeate carrier, wherein the spiral wound membrane element has adiameter of approximately 6 inches or less and a length of approximately18 inches or less. In one option, the membrane element can have adiameter of approximately 3 inches or less.

In one embodiment, the system can include a housing assembly, an inleton the assembly to receive feed water, a prefilter member communicatingwith the inlet to receive the feed water from the inlet, a pair ofmembrane elements both communicating with an outlet of the prefilter toreceive the feed water from the prefilter member, each membrane elementhaving a concentrate outlet and a permeate outlet, wherein each of thepermeate outlets is connected to a faucet without an intervening storagetank, each membrane element including a membrane device including asingle leaf structure which includes a first membrane and a secondmembrane separated by a permeate carrier.

In one embodiment, the system can include a housing assembly, an inleton the assembly to receive feedwater, a prefilter member communicatingwith the inlet to receive the feed water from the inlet, and a pair ofmembrane elements both communicating with an outlet of the prefilter toreceive the feed water from the prefilter member, each membrane elementhaving a concentrate outlet and a permeate outlet, wherein the permeateoutlet is connected to a faucet without an intervening storage tank,each membrane element including a membrane device including a leafstructure which includes a first membrane and a second membraneseparated by a permeate carrier, wherein the membrane device has anouter diameter of approximately 6 inches or less and a length ofapproximately 18 inches or less, wherein the membrane device has a Bvalue of at least about 0.75.

In one embodiment, the system can include a membrane element having afeed water inlet, a permeate outlet connected to a permeate outlet line,and a concentrate outlet connected to a concentrate outlet line, whereinthe permeate outlet is connected to a faucet without an interveningstorage tank, and an automatic shut-off valve coupled to the concentrateoutlet line and the permeate outlet line and located such that theautomatic shut-off valve opens and closes due to the pressuredifferential between the permeate outlet line and the concentrate outletline.

All publications, patents, and patent documents mentioned herein areincorporated by reference herein, as though individually incorporated byreference. It is understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1. A reverse osmosis (RO) system comprising: a housing; a first end cap at one end of the housing; a second end cap at an opposing end of the housing; a pre-filter within the housing such that feed water flows through the first end cap into the pre-filter and exits the pre-filter into the first end cap; a membrane element within the housing such that the pre-filtered water flows from the first end cap and enters the membrane element, wherein permeate and concentrate exit the membrane element into the second end cap; and a shut off valve within the second end cap such that permeate and concentrate flow through the shut off valve.
 2. The reverse osmosis (RO) system of claim 1 wherein the shut off valve allows permeate and concentrate to flow from the second end cap through the housing such that the permeate and concentrate exit the housing through the first end cap.
 3. The reverse osmosis (RO) system of claim 1 wherein the housing includes a permeate outlet line such that permeate flows from the shut off valve in the second end cap through the permeate outlet line to the first end cap, and wherein the housing includes a concentrate outlet line such that concentrate flows from the shut off valve in the second end cap through the concentrate outlet line to the first end cap.
 4. The reverse osmosis (RO) system of claim 1 wherein the membrane element includes a first membrane and a second membrane.
 5. The reverse osmosis (RO) system of claim 4 wherein the first end cap covers an end of the pre-filter and ends of the first and second membranes.
 6. The reverse osmosis (RO) system of claim 4 wherein the first membrane and the second membrane are configured within the housing such that pre-filtered water flows from the first end cap through the first and second membranes in parallel.
 7. The reverse osmosis (RO) system of claim 1 wherein the shut off valve allows concentrate to flow from the membrane element only when permeate is flowing from the membrane element.
 8. The reverse osmosis (RO) system of claim 1 further comprising a faucet to dispense the permeate.
 9. The reverse osmosis (RO) system of claim 1 wherein the housing has a triangular cross-section.
 10. The reverse osmosis (RO) system of claim 1 further comprising a retaining member to mount the first end cap to the housing. 